Method of obtaining predetermined physical constitution in iron



Apnl 19, y1949. H. A. REI-:CE 2,467,406

METHOD OF OBTINING PREDETERMINED PHYSICAL CONSTITUTION IN IRON Filedsept. 25, 194e IN V EN TOR.

Patented Apr. 1949 animos METHOD OF OBTAIN-ING PREDETERIVIINED PHYSICALCONSTITUTION IN IRON Herbert A. Reece, Cleveland Heights, OhioContinuation of application Serial No. 617,747,

September 21, 1945. This application September 25, 1946, Serial No.699,200

.s claims. (ci. '1s-13o) This invention relates to the production ofiron for use in the manufacture of cast iron products and, as one of itsobjects, aims to provide a method by which a base iron having apredetermined physical constitution can be uniformly obtained.

It has been recognized that when a base iron of a given physicalconstitution is subjected to graphitization or other known process stepsand castings are poured from the treated or processed iron, they willhave a desired tensile strength and certain other desirable physicalproperties but, so far as- I am aware, there has never been heretoforeany known way of obtaining a base iron for such subsequent treatmentwhich will uniformly have a desired predetermined physical constitution.Because of the inability heretofore to control the physical constitutionof the base iron, the castings obtained from the processed iron did notuniformly possess the desired physical properties.

By the present invention it is possible to uniformly obtain apredetermined physical constitution in a base iron and since thisphysical constitution of the iron is retained through subsequentgraphitization steps, or other process steps, the castings poured fromthe processed iron will inherit the desired physical constitution andwill therefore possess corresponding desirable physical properties. Inaccordance with this invention the predetermined physical constitutionis obtained in the base iron by controlling the combined carbon contentof the materials charged into the melting furnace.

Another object of the invention is, therefore, to provide a method forcontrolling the physical construction in a base ironby controlling theamount of combined carbon charged into the melting furnace.

Other objects and advantages of the present invention will b e apparentfrom the following description and "the yaccompanying drawing.

'Ihis application is a continuation of my earlier application SerialNo.'617,747, led September 21, 1945, now abandoned.

In the accompanying drawing Fig. 1 is a diagram illustrating the4resultant tensile strength in iron castings where the physicalconstitution of the base iron is not controllable.

Fig. 2 is another diagram illustrating the resultant tensile strength iniron castings when the physical properties as regards tensile strengthare based on total carbon and silicon percentage values, and

Figs. 3-6, inclusive, are diagrams showing the uniformity of resultsobtainable in the physical constitution of base irons by controlling thecombined carbon content of the mixture of ferrous materials charged intothe furnace.

As already indicated in a general way above, v

a feature of prime importance in the `present invention is the discoveryby this applicant that predetermined and can be conveniently designatedby values expressed in terms of the measureto an".

ment of the carbide formation of the iron. In obtaining this measurementa casting of wedgeshaped cross section is first poured from a base ironwhose physical constitutional value is to be determined. Thewedge-shaped casting has an acute angle at its apex defining a.knife-edge and which angle may range approximately from 20 The back faceof the wedge-shaped cast- `ing can be of any convenient width such as1",

2", 3" or 4". This wedge-shape has been found to be very convenient forobtaining the desired measurement but obviously this inventioncontemplates that other shapes could be employed.

After the wedge-shaped casting is poured and has cooled, it is broken intwo transversely so that the carbide balance may be observed on thebroken surface of the casting at the line of demarcation between themetal of white apearance and the metal of grey appearance. The widthmeasured across the broken surface of the wedgeshaped casting at theline of demarcation is taken as an indication of the physicalconstitution of the base iron and the indication or value t thusobtained is usually expressed in for convenience and is referred to as'the constitutional carbide wedge value of the iron.

Generally speaking, a melter operating a metal- A '4 -f centages of thetotal carbon and silicon content are indicated by the plotted points Il.The tensile strength values plotted in Fig. 2 were also obtained fromtests made on standard 1.21" seglurgical furnace has at his disposal'avariety of 5 tion test bars conforming to the specications of rawmaterials such as those represented by the the American Society forTesting Materials and following tabulation and which contain. theperknown thereunder as B bars. centages of combined carbon, graphiticcarbon The iron on which the tests of Fig. 2 were made and total carbonspecied therein. was in the form of castings or test bars havingApproximatsla'omtages anime-ai 1 combined o from Carbon man Carbon s'of'ff .30:0 .so *.soto '.00 flusuuawnmdrmo-rnnrmm. .ino .20 .uw .u:,aorstooxmosmmgoto .10m .00 .1000 .00 n. con summum scoonooo... .e zo1.15 .e0 zo 1.13 aoustook no .aototvo .soto .70 Llsuolgmlnmozo .1000 .40.1Mo .03 .0200 '.20 morons 1.00xoa40 .esto .00 morons l1.30ioa00 .0000.43 1.0000170 1.0000040 .atomo asoman 3.4500020 .30:o1.00 .00:02.401.000oa00 .00:03.00 .40002.00 aootoaoo .esto .s0 100003.10 azotoaw .zato.1s aoszoaus 3.100oa00 .-0000 .00 0:03.00 0:03.00 .soto .10l zooltoaioanomalo .2000 .so acuosa morosa: .30 to .ao 2.40 to aio aio zo 0.00

Pceenltegedvarlosyitlh alloy points Il. The tensile strength valuesplotted in y Fig. 1 were obtained from tests made on standard 1.21lsection test bars conforming to thespeclilcations` of 'the AmericanSociety for Testing Materials and known thereunder as B bars.

The ironon which the tests of F18. 1 rwere made was obtained fromfurnace charges which, as indicated in the legend of Fig. 1, containedsteel approximately 65% to,80%, siliconapproxi- 'mately 1.20% to 1.90%and total carbon approximately .98% to 1.89%. The distribution of theplotted points Il shows that in most cases an iron having aconstitutional carbide wedge value above lhi will have a tensilestrengthv above 50,000#

p. s. i. and this is represented in the diagram by the fact that themalority of the. plottedpoints lie within the area deilned by theangular line AB. It isfimportant to note,however, that the plottedpointslying within this area are scattered and do not conform to any definitepattern. This shows that tensile strenlths above 50,000# p. s. i. areconsistently obtainable when the physical constitution of the base ironis controlled.

The diagram of Fig. 2 illustrates the lack of uniformity in the physicalproperties if iron castings when the iron from which they are obtainedis controlled on the basis of the total carbon and silicon analyses inthe resultant castings or test bars. In this diagram ytensile strengthvalues expressed in 1000# p. s. i. are plotted against the total carbonand silicon content of the test bars expressed as a percentage. Thetensile a total carbon and silicon analysis ranging from about 4.30% toabout 4.85% and which charges,-

as indicated in the legend of Fig. 2, `contained steel approximately 65%to 80%, silicon approximately'1.20%to 1.90% and total carbonapproxivmately .98% to 1.80%. The wide dispersion of 40 the plottedpoints Il shows that there is no cor-- relation between the tensilestrength of an iron and the percentage. value of its total carbon andsilicon content.

' Previous to ,this invention consideration has been given only to thetotal carbon content in the making' up of the furnacewcharge. Underlthat practice it has generallyA been assumed that when the variouscharges all have the sametotal carbon content. `the physicalconstitution of the castings obtained "wond be me same providing mamborecarburiiation value remains the same for all of the melts and that thecupola is operated in a stantially the same total carbon content isclearly indicated by the following examples designated 1 and 2.

:sample 1 00 Steel, .1303#.=61%

Auto cast. 383#=18% Returns, 317#-4.=16%% Spelgel s5#=.45%` Total carboncharged==l.52%

35 Total carbon of me1t=3.02% v Example 2 Steel, 1050#=l0% 1 Pig ironss0#=2s.33%

strength values corresponding with certain per- 7 Silvery, #:=6.07%

Total carbon.charged=1.53%

Total carbon of melt=8.00%

Constitutional carbide wedge values varied from 10 /n to M. l

The result given above in Example 1 were obtained over a period of amonths operation of the cupola during which a large number of tests weremade and the results of Example 2 were obtained from a correspondingnumber of tests performed during a like period of time. From thetabulations given in these two examples it will be seen that the totalcarbon content of the charges are almost identical in value but that theconstitutional carbide wedge values of the irons diifer widely whichshows denitely that the physical constitutions of the melts are not thesame and that the control of the total carbon content of the charge didnot provide an accurate control for the physical constitution of themelt.

The reason for the variance in the constitutional carbide wedge Valuesobtained in Examples 1 and 2 was found to bedue to the inclusion ofvarious types of steels in the materials constituting the charge. Theseexamples demonstrate that the total carbon content of the chargedmaterials is not the controlling element in sey` jcuring a desiredpredetermined physical constitution in the iron.

In analyzing the relationship of the graphitic carbon content to thephysical constitution of a base iron numerous tests were made and theresults set out in the following tabulation, designated Example 3, areillustrative thereof.

Example 3 Graphitic Carbon Constitutional Carbide Wedge Values in lfmContent of Charges,

percent The foregoing tabulation of Example 3 lists the constitutionalcarbide Wedge values ygiven by base irons obtained from charges havingthe percentages of graphitic carbon which are indicated in the example.The wide variation in the graphitic carbon content for charges whichproduced base irons having the same constitutional Example 4 Chargeconsisting of:

Pounds Pig iron 100 Silvery 80 Spiegel 20 Returns 195 Rail steel 500Misc. steel 305 Total 1200 Calc. combined carbon .61% calc. .76% silicon1.43%.

graphitic carbon Calc. combined carbon 80%; calc. graphitic carbon 1.20%:silicon 1.64%.

In Example 4 the charge consisted-of the ferrous materials listed inthis example which aggregated 1200# and had a calculated combinedAcarbon content of approximately .61%, a calculated graphitic carboncontent of approximately .75% and a silicon content of approximately1.43%. In Example 5 the charge consisted of. the same kinds of ferrousmaterials having the same aggregate weight but with the weights of theindividual materials differing considerably from the weights of thecorresponding individual materials in Example 4. The materialsconstituting the charge of Example 5 had a calculated combined carboncontent of approximately .60%, a calculated graphiticcarbon content ofapproximately 1.20% and a silicon content of approximately 1.64%.

An important factor to be noted in Examples 4 and 5 is the fact that thematerials have been so selected that the combined carbon content issubstantially the same in both exampleseven though the other percentagesand the amounts of the individual materials vary widely. Charges asrepresented by Example 4 yielded regularly a base iron with aconstitutional carbide wedge value of 19/32 and charges correspondingwith Example 5 yielded regularly a base iron with a constitutionalcarbide Wedge value of 16/s:. The results 'represented in these examplestherefore clearly show that Iby controlling the combined carbon contentof the materials of the charge a desired calculated percentages ofapproximately .30% to l .60% for the combined carbon content of thematerials charged in the furnace when using in the charge approximately35% to 50% of steel, approximately 1.50% to 2.00% of silicon, and ap'-proximately 1.60% to 2.65% for the total carbon content.

The diagram of Fig. 4 illustrates the use of typical calculatedpercentages of approximately .35% to .65% for the combined carboncontent of the materials charged in the furnace and the resultingconstitutional carbide wedge values as represented by the plotted pointsI 3 when using in lthe charged materials approximately 50% to 65% steel,approximately 1.40% to 2.00% of silicon, and a total carbon content ofapproximately 1.10% to 1.90%.

The diagram of Fig. 5 illustra-tes the use o! typical calculatedpercentages 0f approximately wcm .50% to .80% for thev combined carboncontent resulting constitutionalcarbide wedge values as represented bythe plotted points l5 when using in the charged materials approximately60% to 80% steel. approximately .80% to 1.20% of silicon. and a totalcarbon content of approximately .96% to 1.58%.

Obviously. if the total carbon content of a charge of metal is a fixedvalue, any decrease in the graphitic carbon centen-t results in an'increase in the combined carbon content,` with a resultant increase inthe constitutional carbide value as shown in Figures 3-6. This can beillustrated, by referring to Figure 5, using a iixed total carboncontent of the metal charge of 1.25%

` Per cent Total carbon n 1.25 lGraphitic carbon .60

Combined carbon Constitutional carbide wedge value="/n.l

.'15 Constitutional carbide wedge valu`e=/as.

In the diagrams of 'Figa 3 to 6 inclusive the -plotted points have adefinite pattern in which 'substantially all of the points lie between aPair of parallel sloping lines I6 and I1 which show that the physicalconstitution of the base iron is directly related to and dependent uponthe combined carbon content ofthe materials 0f the charge. The upperline i8 corresponds with a j low steel-high silicon value for thepercentages specified for the materials of the charges in Figs. 3 to 6inclusive and the lower line II corresponds with a high steel-lowsilicon value for the speci-` ned percentages. The slope of the lines Iland Il can be varied by altering the silicon content or the steelpercentages of the charge but the principle of the invention will remainthe sarne.

From the drawing 'and .the foregoing specincation it will now beunderstood that this invention provides a practical and workable methodby which a predetermined physical constitution can be readily anduniformly obtained in a base iron, and hence, iron castings havingdesired physical properties can be uniformly produced when the bese ironis processed. v i

The Iterm cast iron as used herein is intende'd to mean iron products asdistinguished from steel products, that is, iron products containing1.8% to 4.5% carbon and more than .25% silicon.

and which include all of the commonly known cast irons such as gray castiron, white cast iron, air furnace iron, chilled iron, alloy iron.mottled iron, semi-steel and the various trade name irons.r

Although the invention has been disclosed herein in a detailed way itshould not be regarded as being correspondingly limited since it isintended to include all changes and modifications coming within thescope ofthe appended claims.

. y 8l Iclaimasmyinvention: 1. Themethod of producing cast iron trolledphysical properties which comprises chargwedge values being related asshown in Figure I of the drawing, the relationship of the steel andsilicon charges being shown by lines Il and Il of saidilgure withlinellbeinglowsteelandhigh silicon velue and line I'I being high steel andlo' silicon value, melting said charge, and casting' the' molten iron.

2. The method of producing cast iron of controlled physical propertieswhich comprhes charging into a cupalo 1|.v mixture of ferrous materialswhich will provide a predetermined approximate percentage of 50 to 65percent for the steel content of the materials charged, 1.40 to 2.00percent forthe silicon `content and 1.10 to 1.90 percent for the totalcarbon content, and said selected ferrous materials also providing apredetermined approximate percentage oi' .35 to .65 percent for thecombined carbon content of the materials charged such that said mixturewill substantially uniformly give corresponding approximateconstitutlona1 carbide wedge values of '/:z to zuha, the steel charge.the silicon charge, the combined carbon, and constitutional carbidewedge values being related as shown in Figure 4 of the drawing, therelationship of the steel and silicon charges being shown by lines I8and Il of said ligure with line I 6 being low steel and high silicon andline il beinghigh steel and low silicon, melting said charge, and`casting the molten iron.

8. The method of producing cast iron of controlled physical propertieswhich comprises charginginto a cupola a mixture of ferrousm terialswhich will provide a predtermined approximate percentage of 65 to 80percent for the steel content of the materials charged, 1.20 to 1.90percent for the silicon content and .98 to 1.89 percent for the totalcarbon content, and said selected ferrous materials also providing apredetermined approximate percentage of .50 to .80 percent for thecombined carbon` content of the materials charged such that said mixturewill substantially uniformly give corresponding approximateconstitutional carbide wedge values of^192 to 2%2, the steel charge, thesilicon charge, the combined carbon, and constitutional carbide wedgevalues being related as shown in Figure 5 of the drawing. the.relationship of the steel and silicon charges being shown by lines I6and Il of said gure with line i8 being low steel and high silicon andline Il being high steel and low silicon, melting said charge, andcasting the molten iron.

4. The method of producing cast iron of controlled physical propertieswhich comprises charging into a cupola a mixture oi' ferrous materialswhich will provide a predeterminedapproximatepercentageof35toiiopercentforthe` Near..

steel content of the materials charged, .80 to 2.00 percent for thesilicon content and .96 to 2.65 percent for the total carbon content,and said selected ferrous materials also providing a predeterminedapproximate percentage of .30 to .90 percent for the combined carboncontent of the materials charged such that said mixture willsubstantially uniformly give corresponding approximate constitutionalcarbide wedge values 0i 5&2 to 4%2, the steel charge, the siliconcharge, the combined carbon, and constitutional carbide wedge valuesbeing related as shown in Figures 3 to 6 of the drawing, therelationship of the steel and silicon charges being shown by lines I6and I1 of said figures with line I6 being low steel and high silicon andline I1 being high steel and low silicon, melting said charge, andcasting the molten iron.

5. The method of producing cast iron .of con- 10 trolled physicalproperties in which the base molten iron of the character described inclaim 4 is treated by dissolving a. graphitizing material therein.

6. The method of producing cast iron of controlled physical propertiesin which the base iron of the character described in claim 4 is treatedby dissolving a hardening material therein.

HERBERT A.v REECE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,371,654 Smalley et al. Mar. 20,1945

